3-Pentenenitrile (3PN) is produced commercially by the hydrocyanation of butadiene in the presence of nickel catalysts: EQU CH.sub.2 .dbd.CH--CH.dbd.CH.sub.2 +HCN.fwdarw.CH.sub.3 --CH.dbd.CH--CH.sub.2 --CN
3PN is a precursor for the production of the nylon intermediates, adiponitrile (by further hydrocyanation), or adipic acid and caprolactam (by carbonylation to 5-cyanovaleric acid). To form these intermediates, 3PN must first be converted to the terminal olefinic isomer, 4-pentenenitrile (4PN): EQU CH.sub.3 --CH.dbd.CH--CH.sub.2 --CN.fwdarw.CH.sub.2 .dbd.CH--CH.sub.2 --CH.sub.2 --CN
Some hydrocyanation catalysts are also effective for this isomerization, allowing the selective production of adiponitrile commercially by hydrocyanation of 3PN: EQU CH.sub.3 --CH.dbd.CH--CH.sub.2 --CN.fwdarw.[CH.sub.2 .dbd.CH--CH.sub.2 --CH.sub.2 --CN].fwdarw.NC--CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --CN
However, carbonylation catalysts are, in general, relatively poor isomerization catalysts and they are also less selective in the carbonylation of internal vs terminal double bonds. These factors lead to lower yields of 5-cyanovaleric acid and its esters in the carbonylation of 3PN. In contrast, much higher selectivity to 5-cyanovaleric acid can be obtained by carbonylation of 4PN: EQU CH.sub.2 .dbd.CH--CH.sub.2 --CH.sub.2 --CN+CO+ROH.fwdarw.RO.sub.2 C--CH.sub.2 --CH.sub.2 --CH.sub.2 --CH.sub.2 --CN
The present invention is concerned with the isomerization of 3-pentenenitrile to 4-pentenenitrile.
U.S. Pat. No. 3,542,847 to Drinkard et al. discloses the isomerization of 3-pentenenitrile to 4-pentenenitrile by the use of homogeneous palladium or platinum catalysts having a valence of plus 2 or less; and when the platinum or palladium is a zero valent state, an acid is preferably also present.
It is also known from U.S. Pat. No. 4,529,815 to prepare 4-pentenoates using an acidic ion-exchange resin or zeolite containing a noble metal of group 8 of the periodic table as the catalyst.
Perfluorinated ion-exchange resins have been previously employed as isomerization catalysts--see, for example, U.S. Pat. Nos. 4,022,847 and 4,038,213 to McClure and McClure et al. which disclose the isomerization of alkanes.